An expectant mother is examined by a midwife during a home visit in Free Union, Va, in November 2005. / File photo by Andrew Shurtleff, AP

by Liz Szabo, USA TODAY

by Liz Szabo, USA TODAY

A new treatment approach increases the odds that women with a common cause of infertility can have a baby.

The study focused on women with polycystic ovary syndrome, or PCOS, one of the most common causes of infertility in women. PCOS affects about 5% to 10% of women, who develop multiple cysts on their ovaries and often have irregular periods, according to the study, published Wednesday in The New England Journal of Medicine.

Doctors have prescribed the drug clomiphene for years to help these women conceive, but pregnancy rates remain low, with only about one in five getting pregnant after six treatment cycles.

In the new study of 750 women, doctors compared clomiphene with another drug, letrozole, which is commonly used as a breast cancer treatment in postmenopausal women whose cancers are fueled by estrogen, says Richard Legro, the study's first author and a professor at Penn State College of Medicine.

About 28% of women randomly assigned to take letrozole had a live birth, compared with 19% of those assigned to take clomiphene, according to the study, funded by the National Institutes of Health. Women underwent up to five monthly treatment cycles with either drug.

There were no significant differences in the rate of twins and triplets, miscarriages or birth defects, the study says. The two drugs caused different side effects. Among those taking clomiphene, 33% of women developed hot flashes, 15% had fatigue, and 8% suffered from dizziness.

Among those taking letrozole, 22% had fatigue, 20% had hot flashes, and 12% experienced dizziness, according to the study.

The results are likely to change medical practice, encouraging doctors to try letrozole first, says Charles Coddington, a professor at Minnesota's Mayo Clinic and president of the Society for Assisted Reproductive Technology, who was not involved in the study.

Today, doctors typically start with clomiphene, mostly because its side effects and safety are well-established, then switch to letrozole only if women don't conceive, Coddington says.

Now that letrozole appears safe, more doctors will feel comfortable using it, says Samantha Butts, associate professor of obstetrics and gynecology at the Hospital of the University of Pennsylvania.

Both clomiphene and letrozole are much less expensive than other treatment options, Coddington says. A cycle of these drugs, combined with ultrasounds and blood tests, costs about $300.

In comparison, a month's treatment with injectable fertility drugs costs around $1,000. In vitro fertilization, or IVF, costs about $15,000 per attempt, Coddington says.

Legro cautions that doctors should try to confirm his results with additional studies. He says doctors also to need follow babies long term, to confirm there is no increased risk of birth defects from letrozole.